The Practices - Agroecology in Action - page 143

Table 5.5
Potential benefits and drawbacks of cover crops.

Potential benefits Potential drawbacks

Improved soil structure Increased water use

Improved water infiltration Competition for moisture and

nutrients

Improved tractor wheel traction Increased frost hazard

Addition or conservation of nitrogen Habitat for vertebrate pests

Addition of carbon and organic matter Increased time needed to manage

Dust reduction to reduce mite outbreaks Increased costs

Control of soil erosion and nutrient run-off

site specific needs of their fields' soils. Growers seeking a single benefit
previously provided by a single agrochemical product are disappointed.
Growers who have developed the eye to see incremental, cumulative and
multiple benefits over time have made cover crops a centerpiece of their
soil and nutrient management.
Growers of winegrapes have found cover crops to be compatible with
winegrape growing for several reasons, and the result is that 15-30
percent of them use cover crops. 24 Vineyards on hillsides have historically
used cover crops to control erosion. 25 Grape vines have modest nitrogen
needs—roughly 25 percent of the per acre requirements of rice or
walnuts—which can be provided easily by leguminous cover crops.
Researchers thoroughly documented the problems associated with excess
nitrogen in vineyards: over-application of nitrogen to grape vines can
result in excessive vigor, which stimulates canopy growth shading the
fruit, creates a favorable microclimate for pests and disease, and
decreases fruit quality. Cover crops, or at least resident vegetation, help
this strategy to reduce vine vigor by providing competition. This is an
example of the multiple, indirect benefits that cover crops provide.
The annual and animal crop partnerships, more than those in peren-
nial crops, tended to put emphasis on soil, fertility, and irrigation
techniques. The field-crop BIFS partnership developed new cultivation
and soil fertility management techniques. 26 Pre-plant tillage accounts
for more than one-fifth of total production costs, so the partnership
analyzed various biological inputs and reduced tillage strategies. This
partnership had to adapt conservation tillage principles to local